Plate clamping mechanism for printing cylinder

ABSTRACT

An underside plate clamping mechanism for securing printing plates to a plate cylinder of a printing machine is disclosed in which the leading side of the plate is held and positioned by adjustable register fingers protruding above the surface of the printing cylinder and the trailing side of the plate is tensioned by spring-biased clamping fingers protruding above the surface of the cylinder. The register fingers of the plate clamping mechanism are formed on an integral (monolithic) member arranged in a longitudinal groove in the interior of the printing cylinder and are pivoted for rotation about an axis offset from and parallel to the axis of the printing cylinder. Resilient means are provided for biasing the integral member in a direction of rotation tending to release the register fingers from engagement with the printing plate. Screw means are provided for applying a positive force to the integral member in a direction of rotation tending to engage the register fingers with the printing plate. The clamping fingers at the trailing side of the plate are each arranged on a finger block which is movable linearly in a direction transverse to the rotational axis of the printing cylinder. The finger blocks are each mounted on an actuating block which is movable axially in the printing cylinder. Axial movement of the actuating blocks is translated into transverse movement of the finger blocks by angled engaging teeth on the abutting surfaces of the actuating and finger blocks. An actuating rod, arranged in a longitudinal groove of the printing cylinder, and axially movable between plate clamping and plate releasing positions, is provided to apply an axial biasing force to all the actuating blocks. The actuating blocks are resiliently mounted on the actuating rod to allow for limited movement of the plate.

[22] Filed:

United States Patent 1 1 Porter 1 1 PLATE CLAMPING MECHANISM FOR PRINTING CYLINDER [75] Inventor: Clive Porter, York, Pa.

[73] Assignee: Motter Printing Press Co., York, Pa.

Dec. 10, 1973 [21] Appl. No.: 423,243

Related US. Application Data [63] Continuation of Ser. No. 297,920, Oct. 16, 1972,

Primary Examinew-Edgar S. Burr Assistant E.\'uminerPaul .1. Hirsch Attorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond 57; ABSTRACT An underside plate clamping mechanism for securing 1 Sept. 30, 1975 printing plates to a plate cylinder of a printing machine is disclosed in which the leading side of the plate is held and positioned by adjustable register fingers protruding above the surface of the printing cylinder and the trailing side of the plate is tensioned by springbiased clamping fingers protruding above the surface of the cylinder. The register fingers of the plate clamping mechanism are formed on an integral (monolithic) member arranged in a longitudinal groove in the interior of the printing cylinder and are pivoted for rotation about an axis offset from and parallel to the axis of the printing cylinder. Resilient means are provided for biasing the integral member in a direction of rotation tending to release the register fingers from engagement with the printing plate. Screw means are provided forvapplying a positive force to the integral member in a direction of rotation tending to engage the register fingers with the printing plate. The clamping fingers at the trailing side of the plate are each arranged on a finger block which is movable linearly in a direction transverse to the rotational axis of the printing cylinder. The finger blocks are each mounted on an actuating block which is movable axially in the printing cylinder. Axial movement of the actuating blocks is translated into transverse movement of the finger blocks by angled engaging teeth on the abutting surfaces of the actuating and finger blocks. An actuating rod. arranged in a longitudinal groove of the printing cylinder, and axially movable between plate clamping and plate releasing positions, is provided to apply an axial biasing force to all the actuating blocks. The actuating blocks are resiliently mounted on the actuating rod to allow for limited movement of the plate.

1 Claim, 8 Drawing Figures U.S.. Patent Sept. 30,1975

Sheet 1 of5 3 9%,546

U.S. Patent Sept. 30,1975 Sheet 2 of5 3,908,546

m mI,

US. Patent Sept. 30,1975 Sheet 5 of5 3 985 (III PLATE CLAMPING MECHANISM FOR PRINTING CYLINDER This is a continuation of application Ser. No.

297,920, filed Oct. 16, 1972, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a plate clamping mechanism for a printing machine. More particularly, the present invention is concerned with clamping mechanisms for securing printing plates to a printing cylinder of a printing machine.

A number of clamping mechanisms for printing cylinders are known. One example of such a mechanism used two fingers to hold each respective side of a printing plate, with each finger capable of being moved circumferentially around the cylinder. The movement of the fingers was produced by rotation of two separate shafts placed within the interior of the cylinder and joined to their respective finger members by gear and tooth means. Such a device allowed for adjustment of the fingers to securely hold a printing plate prior to initiation of the printing cycle but did not provide for resilient movement of at least one of the fingers when in its adjusted position in response to either slippage or deformation of the plate during the printing cycle to hold the plate securely on the cylinder.

In order to overcome this disadvantage, an apparatus was devised which used rigid clamping fingers at the leading side of the printing plate and spring biased clamping fingers at the trailing side. This allowed for resilient engagement of the clamping fingers with the trailing side of the plate to allow for slight changes in the dimensions or shape of the plate during printing. The clamping fingers at both sides of the plate were designed for concentric movement about the axis of the printing cylinder and were adapted to be moved into and out of clamping position by the action of axially movable operating rods which were actuated by a wrench inserted in the cylinder at the end of the printing plate. Axial movement of the operating rods in this apparatus was transmitted to the respective clamping fingers by axially movable block members, joined to rods, which engaged the underside of the clamping teeth through helical gears.

The last-mentioned apparatus has a number of disadvantages. It was rather complicated in construction thereby increasing the cost for its manufacture and raising the likelihood of a greater chance of mechanical failure of one of its components. During manufacture, it was difficult to insure accurate placement of the axially movable blocks on the axially movable operating rod so that accurate placement of the clamping fingers in the desired location was difficult. The apparatus, by

providing for circumferential movement of the clamping fingers between plate clamping and plate releasing positions, required that in the manufacture of the device the surface of the finger members as well as the engaging portion of the cooperating blocks inside the printing cylinder had to be machined in a rounded shape, i.e., cooperating concave and convex configurations, to insure the desired movement. Such machining was quite difficult and expensive. Finally, the apparatus contained a plurality of clamping fingers across the width of the clamping mechanism with a single means at the end of the clamping mechanism to adjust all its fingers simultaneously. Ifmore than two clamping mechanisms were arranged longitudinally along the length of the printing cylinder, as was often required, the adjusting means had to be placed between adjacent clamping mechanisms thereby spacing the respective mechanisms further. apart. This type of design precluded printing on portions of a paper web lying over the adjustment means and resulted in a waste of paper. The apparatus of the present invention is designed to overcome these and other disadvantages of prior art apparatus.

Representative examples of prior art plate clamping apparatus are described in the following patents: Faeber U.S. Pat. No. 2,621,590; McWhorter U.S. Pat. No. 2,668,497; Crafts U.S. Pat. No. 2,679,802; McWhorter U.S. Pat. No. 2,709,405; Knowles U.S. Pat. No. 2,709,406; Krueger U.S. Pat. No. 2,928,161; Ringe et a1. U.S. Pat. No. 3,019,729; Peabody et a1. U.S. Pat. No. 3,095,811; Tyma et al. U.S. Pat. No. 3,127,834; Doyle et al. U.S. Pat. No. 3,202,097.; Harenza U.S. Pat. No. 3,335,663; Ringe U.S. Pat. No. 3,515,066; Tafel U.S. Pat. No. 3,534,694; and Luehrs U.S. Pat. No. 3,538,850.

SUMMARY OF THE INVENTION U The clamping mechanism of the present invention has a first lock-up means which is arranged in a longitudinal groove in'the printing cylinder for securing the leading side of a printing plate to the printing cylinder. The first lock-up means comprises an integral (monolithic) member which is arranged in the longitudinal groove and which is pivoted for rotation about an axis offset from and parallel to the axis to the printing cylinder. The integral member has a plurality of register fingers each of which protrudes above the surface of the printing cylinder and each of which is arranged to engage the printing plate in a recess in its underside. This first lock-up means also comprises a resilient means, such as a spring, for biasing the integral member in a direction of rotation tendingto release its register fingers from engagement with the recess of the printing plate. Screw means are provided in the first lock-up means for applying a positive force to the integral member in a direction of rotation which tends to engage its register fingers with a recess formed in the back of the printing plate to hold the plate on the cylinder. The screw means are accessible for turning from the surface of the printing cylinder, and when turned, can be used to vary the position of the register fingers.

The mechanism also comprises a second lock-up means which is arranged in a second longitudinal groove in the printing cylinder for securing the trailing side of the printing plate to the printing cylinder. The second lock-up means comprises an actuating rod arranged in the groove along an axis which is offset from and parallel to the axis of the printing cylinder. This rod is movable axially between a plate clamping and a plate releasing position. Disposed at intervals along the actuating rod are a plurality of actuating blocks which have engaging surfaces on their outer side which extend substantially radially with respect to the printing cylinder and at an angle with respect to the axis of the printing cylinder. Resilient means connect the actuating rod with each of the actuating blocks to thereby urge the blocks in an axial direction when the acutating rod is in the plate clamping position. A plurality of finger blocks are included in the second lock-up means. Each finger block has a clamping finger protruding above the surface of the printing plate. Each finger block is associated with and arranged adjacent to the outer side of one of the actuating blocks and each finger block has engaging surfaces on its inner side thereof which extend substantially radially with respect to the printing cylinder and which are angled with respect to the axis of the printing cyylinder. Each of the engaging surfaces on the finger blocks is disposed in facing relationship to a respective one of the engaging surfaces of the associated actuating block to thereby provide for movement of the finger blocks in a direction tending to engage the clamping fingers with a recess in the underside of the printing plate when the actuating blocks are urged in an axial direction. Means are provided which are accessible from the surface of the printing cylinder and which are adapted to be actuated by rotation by a wrench for moving the actuating rod in the second lock-up means between a plate clamping and a plate releasing position.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further understood by reading this specification and the drawings appended herewith wherein:

FIG. 1 is a cross-sectional view of the printing cylinder showing three of the clamping mechanisms of the present invention arranged on the surface of that cylinder;

FIG. 2 is an overhead view showing the mechanism of the present invention;

FIG. 3 is an enlarged overhead view which is paritally cut away and disassembled showing the apparatus of the present invention;

FIG. 4 is a view taken along line 44 of FIG. 3 show ing in section the second lock-up means;

FIG. 5 is a view in section taken along line 55 of FIG. 3 showing the first lock-up means;

FIG. 6 is a view in section taken along line 6-6 of FIG. 3 showing the first and second lock-up means of the present invention;

FIG. 7 is a view taken along line 7-7 of FIG. 3 showing in section the means for moving the actuating rod in the second lock-up means; and

FIG. 8 is an elevational view showing four of the clamping mechanisms of the present invention in sideby-side relationship on a printing cylinder.

DESCRIPTION OF A PREFERRED EMBODIMENT As best seen in FIGS. 1, 2 and 8, the present invention, which is generally designated by reference numeral 11, is a clamping mechanism for securing a printing plate 12 to the surface of a printing cylinder 13, rotatable with an integral journal 14. In a preferred embodiment as shown in FIG. 8, a plurality of clamping mechanisms can be placed in side-by-side relationship on an elongated printing cylinder 13 to hold a number of printing plates 12 in position.

The apparatus 11 of the present invention comprises a first lock-up means 15 for securing the leading side, labeled L in the Figures, of the printing plate 12 to cylinder 13, and a second lock-up means 16 for securing the trailing side, labeled T in the Figures, of printing plate 12 to the cylinder 13. The apparatus of the present invention 11 is placed in a recess 17 in the outer periphery of printing cylinder 13.

The first lock-up means is best understood by referring to FIGS. 3, 5, 6 and 7 of the drawings. The lock-up means 15 is arranged in a longitudinal groove 18 in printing cylinder 13. It comprises an integral member 19 which lies in the longitudinal groove 18 and which is pivoted for rotation about an axis which is offset and parallel to the axis of the printing cylinder 13. The integral member 19 has a plurality of register fingers 20 which each protrude above the surface 21 of the printing cylinder 13 to engage a recess 22 in the underside of the printing plate 12 to hold that plate securely in place on the printing cylinder 13.

As used herein, the term integral member is intended to denote a monolithic member; that is, a member formed (e.g., by casting and milling) from one piece of material, such as steel.

As shown in FIG. 7, the integral member 19 is biased by action of a spring-mounted plug 24 on flange 23 in a direction which is opposite to the direction of rotation of the printing cylinder 13 so as to tend to release the register fingers 20 from engagement with the recess 22 in the printing plate 12.

In order to have the register fingers 20 engage the recess 22 of the plate 12 to the desired degree, a screw 26 in bore 25 is provided in an area lying between the portions of the cylinder adapted to be occupied by the leading and trailing sides of the printing plate and at a point between the outermost ones of the plurality of register fingers 20. This screw 26 can be turned to drive it further into the longitudinal groove holding integral member 19 so that its lower edge 27 is driven against surface 28a of block 28, thereby pivoting the integral member 19 on its fixed mount 32 which is shown in FIG. 3. The block 28 is pivoted at 29 to insure that surfaces 27 and 28a always are parallel when they meet. The operation of pivoting integral member 19 on its mount drives the register fingers 20 into clamping en gagement with the recess 22. Integral with the screw 26 is a fluted portion 33 which holds the screw 26 in the desired location through cooperation with spring mounted ball 35 on the integral member 19. The inte gral member 19 can be machined as a single piece to very close tolerances to insure accurate placement of the integral member and the register fingers 20 in the printing cylinder 13. This is one distinct advantage that the present invention has over a number of prior art clamping mechanisms.

When integral member 19 is pivoted, the register fingers 20 move concentric to the axis of the integral member 19 rather than concentric to the axis of the printing cylinder 13. The fingers 20 will be at their highest elevation above the surface 21 of the printing cylinder when in their neutral position which occurs when their tips lie on a straight line running through the axis of the printing cylinder 13 and the axis of the integral member 19. The extreme position of the register fingers 20 on either side of this neutral position will result in the fingers being no more than about 0.005 inches lower than they are when in the neutral position. This small difference in height does not affect the performance of the register fingers 20 in holding down the leading edge of the printing plate 12.

The second lock-up means which is best seen in FIGS. 3, 4 and 7, is also arranged in a longitudinal groove 34 in the printing cylinder 13 for securing the trailing side, labeled T, of the printing plate 12 to the printing cylinder 13. An actuating rod 36 is arranged in the longitudinal groove 34 along an axis that is offset and parallel to the axis of the printing cylinder 13. This actuating rod is adapted to move axially between a plate clamping and a plate releasing position, and at inand 37a on the actuating rod 36 and a surface 40 on each of the actuating blocks 38 to give the blocks a resilient mounting on the rod. The spring means urge the blocks in an axial direction when the actuating rod is in the plate clamping position. The nuts 37 may be adjusted along the actuating rod 36 to position to the actuating blocks 38 in the direction parallel to the axis of the printing cylinder. The preloacl tension of the spring means 41 is determined by the length of the spacers 36a.

Situated at the outer side of each of the actuating blocks 38 is a finger block 42 which has a clamping finger 46 at its outer surface which protrudes above the surface 21 of printing cylinder 13. The underside of each finger block has engaging surfaces 44 which engage corresponding surfaces 39 in the adjacent actuating block 38. Each of the engaging surfaces 39 and 44 extends along a straight line in its longitudinal direction and substantially radially with respect to the printing cylinder and is angled with respect to the axis of the printing cylinder. The engagement of surfaces 39 in actuating block 38 with the surfaces 44 of the finger block 42 enables the finger block to be moved linearly in a transverse direction which tends to engage clampingfingers 46 with the corresponding recesses 48 underneath the trailing side T of printing plate 12 when the actuating block 38 is urged in the axial direction.

The movement of finger blocks 42 and the integral clamping fingers 46 is linear with respect to the axis of the printing cylinder 13. This will cause a slight variance in the extent to which the fingers 46 protrude above the surface 21 of the printing cylinder 13 as they are moved between their plate clamping and plate re- ;leasing positions. It has been found, however, that the total change in the amount of protrusion is on the order of about 0.0008 inches in a preferred embodiment of the present invention. This change in height of the clamping fingers is smaller than the accuracy to which the recesses 48 of the printing plate 12 are machined v so that it causes no difficulty when the apparatus is used.

Means which are accessible from the surface of printing cylinder 13 are provided tomove the actuating rod 36 between a plate clamping and plate releasing position for clamping fingers 46 FIGS. 4 and 7 best illustrate the means which are used to move the actuating rod. They comprise a crank member 50 which is arranged for rotation about an axis substantially transverse to the axis of actuating rod 36. The crank member has a crank web 52 and a flat-edged knob 54 which is adapted to receive a wrench 56 that can be inserted through an open slot 58 in the surface 21 of printing cylinder 15. The slot 58 lies on a portion of the printing cylinder 13 lying between the areas of the cylinder normally holding the leading and trailing sides of the printing plate 12 and at a'p'oint inside the outermost ones of the plurality of actuating blocks 38. The wrench 56 can be rotated between two limits which are at angles of approximately 45 to a straight line drawn between the axis of the cylinder'13 and the center of the slot 58 to clamp or release the printing plate 12, respectively.

FIG. 4 illustrates how the crank means 50 is moved to either unlock (release) or lock (clamp) a plate to the printing plate cylinder 13. In FIG. 4 the dashed outline of the crank means 50 shows the apparatus in the locked position and the dotted-dashed outline shows the apparatus in the unlocked position. The crank web 52 extends horizontally when the apparatus is in the locked position so that the crank pin contacts the surface 62a on an actuating block 62. The block 62 is connected to the actuating rod 36 by means of a transverse pin 61 so that, in the plate clamping position, the block 62 holds the rod 36 towards the left. Further, upward movement of web 52 is limited by the stop surface 63. A wrench 56 can be inserted as shown when the crank web 52 is in the locked position. In order to unlock the mechanism the wrench is rotated in the direction of the arrow thereby pivoting the crank member 50 and its web 52 until the web 52 extends downwardly and makes contact with the stop surface 60. At this position the actuating rod 36 is forced to its plate releasing position shown in dotted-dashed lines in FIG. 4. The stop surfaces 60 and 63 limit the rotation of crank means 50 to a angle. Due to the biasing force of spring 41 on the actuating block 62, the crank means 50 is urged against the stop means, 63 since the crank means is slightly over dead center.

FIG. 8 is a view showing four of the clamping mecha-' nisms of the present invention in side-by-side relationship on a printing cylinder. As can be readily seen, the placement of bore 25 and slot 58 and the respective means for varying the position of register fingers 20 and clamping fingers 46 between portions of printing cylinder 13 adapted to hold the leading side If and trailing side T of the printing plate 12 enables persons in the art to place printing plates in closer side-by-side relationship than is possible using prior art clamping mechanisms.

Upon reading the foregoing specification and examining the appended drawings, a person of skill in the art will become aware of modifications which can be made to the invention described herein without departing from the spirit and scope of that invention. Hence, the foregoing is intended to be merely illustrative of certain preferred embodiments of the claimed invention and is not to be construed as limiting in any way. The appended claims define the invention.

I claim:

I. A clamping mechanism for securing a printing plate to a printing cylinder comprising, in combination:

a. first lock-up means, arranged in a longitudinal groove in the printing cylinder, for securing the leading side of a printing plate to the printing cylinder, comprising:

i. a monolithic member arranged in the longitudinal groove and pivoted for rotation about an axis offset from and parallel to the axis of the printing cylinder, said monolithic member having two register fingers each protruding above the surface of the printing cylinder and arranged to engage the printing plate in a corresponding recess in the underside of the printing plate, there being two such recesses at the leading side of the printing plate;

ii. resilient means for biasing said monolithic member in a direction of rotation tending to release said register fingers from engagement in the recesses of the printing plate; and

iii. screw means for applying a positive force to said monolithic member in a direction of rotation tending to engage said register fingers with the printing plate in the recesses of the printing plate, said screw means being accessible for rotation from the surface of the printing cylinder and being adjustable, upon rotation, to vary the position of said register fingers; and

printing plate in a corresponding recess in the undersidc of the printing plate, each finger block being associated with and arranged adjacent to said .outer side of one of said actuatingblocks,

b. second lock-up means, arranged in a longitudinal groove in the printing cylinder, for securing the trailing side of a printing plate to the printing cylinder, comprising:

i. an actuating rod arranged in the longitudinal sponding recesses in the underside of the printing plate when said actuating blocks are urged in said axial direction;

v. means accessible from the surface of the printing cylinder for moving said actuating rod between groove along an axis offset from and parallel to the axis of the printing cylinder and movable axif plate cldmpmg and Sald plate releasing ally between a plate clamping and a plate releasf d l h ing position, said actuating rod being threaded dp ura o P Spose at men/a S a f along at least a portion of its length, length of and in threaded engagement with said a plurality of actuating blocks, disposed at interactuaFmg one bemg dlsposed a Vals along Said actuating rod and having engag one side of each actuating block to position said ing surfaces on the outer side thereof extending acfuatlng tflock 9 531d actuatmg 9 f substantially radially with respect to the printing f actuatmg rod 15 plate relasmg P cylinder and angled with respect to the axis of the and one nut beulg P f J each priming cylinder, Said actuating blocks being resilient means to tension said resilient means at provided with a bore of sufficient diameter to acleast w f actuating rod is in the Plate commodate said actuating rod in non-engaging Clampmg Posltlon; and relafionship; vii. spacer means, disposed in the bore of each aciii. resilient means connecting said actuating rod mating block and extending between the nuts on wi h h f id bl k h b urge id opposite sides thereof, for establishing a fixed blocks in an axial direction when said actuating istan etween Said nuts on the Opposite sides rod is in said plate clamping position; .of the actuating block, the length of said spacer iv. a plurality of finger blocks each having a clampmeans thereby determining the preload tension ing finger protruding above the surface of the on said resilient means. printing cylinder and arranged to engage the 

1. A clamping mechanism for securing a printing plate to a printing cylinder comprising, in combination: a. first lock-up means, arranged in a longitudinal groove in the printing cylinder, for securing the leading side of a printing plate to the printing cylinder, comprising: i. a monolithic member arranged in the longitudinal groove and pivoted for rotation about an axis offset from and parallel to the axis of the printing cylinder, said monolithic member having two register fingers each protruding above the surface of the printing cylinder and arranged to engage the printing plate in a corresponding recess in the underside of the printing plate, there being two such recesses at the leading side of the printing plate; ii. resilient means for biasing said monolithic member in a direction of rotation tending to release said register fingers from engagement in the recesses of the printing plate; and iii. screw means for applying a positive force to said monolithic member in a direction of rotation tending to engage said register fingers with the printing plate in the recesses of the printing plate, said screw means being accessible for rotation from the surface of the printing cylinder and being adjustable, upon rotation, to vary the posiTion of said register fingers; and b. second lock-up means, arranged in a longitudinal groove in the printing cylinder, for securing the trailing side of a printing plate to the printing cylinder, comprising: i. an actuating rod arranged in the longitudinal groove along an axis offset from and parallel to the axis of the printing cylinder and movable axially between a plate clamping and a plate releasing position, said actuating rod being threaded along at least a portion of its length; ii. a plurality of actuating blocks, disposed at intervals along said actuating rod, and having engaging surfaces on the outer side thereof extending substantially radially with respect to the printing cylinder and angled with respect to the axis of the printing cylinder, said actuating blocks being provided with a bore of sufficient diameter to accommodate said actuating rod in non-engaging relationship; iii. resilient means connecting said actuating rod with each of said blocks to thereby urge said blocks in an axial direction when said actuating rod is in said plate clamping position; iv. a plurality of finger blocks each having a clamping finger protruding above the surface of the printing cylinder and arranged to engage the printing plate in a corresponding recess in the underside of the printing plate, each finger block being associated with and arranged adjacent to said outer side of one of said actuating blocks, and each finger block having engaging surfaces on the inner side thereof extending substantially radially with respect to the printing cylinder and angled with respect to the axis of the printing cylinder, said engaging surfaces of said finger blocks being disposed in facing relation to respective ones of the engaging surfaces of the associated actuating blocks to thereby move said finger blocks in a direction tending to engage said clamping fingers with the printing plate in corresponding recesses in the underside of the printing plate when said actuating blocks are urged in said axial direction; v. means accessible from the surface of the printing cylinder for moving said actuating rod between said plate clamping and said plate releasing positions; vi. a plurality of nuts disposed at intervals along the length of and in threaded engagement with said actuating rod, one nut being disposed adjacent one side of each actuating block to position said actuating block along said actuating rod when said actuating rod is in the plate releasing position, and one nut being disposed adjacent each resilient means to tension said resilient means at least when said actuating rod is in the plate clamping position; and vii. spacer means, disposed in the bore of each actuating block and extending between the nuts on opposite sides thereof, for establishing a fixed distance between said nuts on the opposite sides of the actuating block, the length of said spacer means thereby determining the preload tension on said resilient means. 